1. Field of the Invention
This invention relates generally to a video signal enhancer for photographic reproduction and, more particularly, to a signal processor for use with a television receiver in order to enhance the video signals for photographic reproduction.
2. Description of the Prior Art
One approach for obtaining a photographic image of a color television image is to directly photograph the screen of a color television using color film. This approach will reproduce the subject matter in a way in which, while satisfactory for some purposes, is of a quality much poorer than that of a direct photograph of the scene being televised in terms of color rendition, contrast, etc. This poor quality results from, among other things, the mismatch in the spectral emission properties of the phosphors of the television cathode ray tube and the spectral sensitivities in the photosensitive layers of the film; and the mismatch between the nonlinear grey scale sensitivity of the film and the generally linear response of the cathode ray tube. Thus, other techniques have been developed which first divide the color television signal into its color separation video signals, i.e., red, blue, and green video signals, and then sequentially display the signals on a monochromatic CRT whose screen is photographed through filters in a way that synchronizes the color of the filter to the color of the video signal being displayed on the screen. Thus, in this technique, color film is exposed through a red filter to the image on the screen of a monochromatic CRT while the red color separation image is displayed, through a blue filter while a blue color separation image is displayed on the CRT and through a green filter while the green color separation image is displayed. The exposure times will depend on the optics, the phosphors of the CRT and the type of film; and, the proper exposure time can be determined by trial and error. While this technique will provide an improved photograph over the quality of an image that is provided by photographing the entire color picture directly from the screen of the cathode ray tube, it still nevertheless requires that the red, green, and blue filters be sequentially moved by mechanical apparatus into place to expose the film to red, green, and blue color separation signals. Thus, the time for taking a photograph is extended, and a mechanical apparatus for moving the filters in this manner must be provided. Although this technique does not encounter the aforementioned difficulties resulting from the spectral emission properties of the cathode ray tube phosphors not matching the spectral sensitivities in the photosensitive layers of the film, it nevertheless fails to compensate for films of high contrast having nonlinear sensitivity curves.
Therefore, it is a primary object of this invention to provide a signal processor for a conventional television receiver in order to enable a photograph to be made directly from the screen of the receiver such that the photographic image is of an appearance substantially corresponding to the appearance of the image otherwise displayed on the screen of the receiver.
It is a further object of this invention to provide a signal processor for use with a conventional television receiver in order to enable the screen of the television receiver to be directly photographed to provide a high quality photographic image without the necessity of sequentially exposing the film through red, green, and blue filters.
Other objects of the invention will be in part obvious and will in part appear hereinafter. The invention accordingly comprises a system possessing a construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure.